1. Field of the Invention
The present invention relates to improved efficiency of mixing and subsequent separation of distillation rising vapors with input feed and in most cases, to achieve lower partial pressure for vaporizing more feed entering the flash zone to increase the yield of more valuable lighter products for constant energy input; or, conversely, reduce energy input for constant yield. It is directed toward a process and an apparatus which involves the use of a mixing and separation chamber at the feed nozzle of the distillation column. The process and apparatus are applicable to any distillation process but are particularly useful in crude oil distillation, primary and secondary distillation.
2. Prior Art Statement
Historically, in a distillation process, a vaporizing feedstock has been fed into the distillation column at what is called the "flash zone" by pressurized injection, typically through a feed flush or tangential nozzle which merely sprayed or otherwise injected the vaporizing feed out over the rising vapors from the fractionation or stripping section located below the flash zone. While this technique was used for a long time and distillation was achieved, it was recognized that much of the hot liquid feed remained as droplets and not all of the feed made contact with all of the rising vapors. The actual efficiency of mixing and contacting the rising vapors with the vaporizing feed was impaired and excessive amounts of the heavy liquid fractions were carried upward to fractionation sections above the flash zone.
Subsequently, it was discovered that the liquid droplets could be more efficiently separated from the feed vapors by introducing the feed through a tangential feed nozzle into an open bottom chamber or baffle which was circumferential. Advantageously, an open bottom chamber was downwardly sloped and did not make a complete turn within the distillation column. It is recognized that the centrifugal motion of the hot feed and the outward (and slightly downward) turbulent spray of the vaporizing feed into the rising vapors coalesced the droplets so that fewer liquid drops are entrained and carried above the flash zone. While this prior art improvement somewhat enhanced the separation of liquid droplets from the rising vapors and feed vapors, it forced most of the droplets to follow the circumferential wall of the flash zone, and did not fully address the problem of large portions of the liquid feed separating from its own forming feed vapors before those feed liquid and vapors mixed with the rising vapors and this resulted in poor contact. Thus, the improved system decreased entrainment of rising droplets but didn't eliminate, and possibly magnified, the problems of "falling" liquid feed and inefficient mixture of feed liquid and vapors with rising vapors from the stripping section below the flash zone.